The invention relates to a fluid-loadable tensioning device for printing forms on rotary printing machines, whether sheet-processing or web-processing rotary printing machines for recto printing, recto/verso printing, newsprinting or also job printing.
The published European Patent Document EP 0 842 773 A1 is concerned with a reusable winding core for rotary printing machines. A reusable winding reel is provided which is intended for a plate cylinder of a rotary printing machine. The winding core is formed of two halfshells which are assembled in a manner for producing two slotlike orifices located opposite one another. Within a tubular sleeve part formed of the two halfshells there is provided a control element which is adjustable so that the outside diameter of the winding core can be changed. Preferably, the winding core is pre-set to an outside diameter so that it becomes possible for plate material to be wound up from a supply reel. In order to disassemble the winding core from the interior of a printing unit cylinder of a rotary printing machine, the winding core diameter can be changed by a control element so that it becomes possible to extract the winding core reel easily from the interior of a plate cylinder of a rotary printing machine. U.S. Pat. No. 5,735,211 is concerned with a clamping and tensioning device for printing forms on rotary printing machines. In the construction described in this patent, the clamping device for holding a printing form in a defined position in relation to a printing form cylinder is received within a tensioning device, by which the clamping device is itself capable of being moved as a whole relative to the surface of the printing form cylinder, in order, on the one hand, to tension the printing form with respect to a tensioning gap or, on the other hand, to detension the printing form on the circumference of the printing form cylinder. A piston arrangement is provided, by which one of the two edges of the printing form can be pressed in the direction of the tensioning gap.
Finally, the published European Patent Document EP 0 884 176 A1 is concerned with a clamping device for a rubber blanket on a transfer cylinder of a rotary printing machine. In this development, a rubber blanket reinforced by a metal layer is tautened onto a transfer cylinder in the printing unit of a rotary printing machine. The rubber blanket to be accepted on the transfer cylinder is formed with a slit. Tensioning edges are formed on the metal layer and can be tensioned in a tensioning gap of a transfer cylinder. A dressing including compressible elastomers is fastened onto the upper side of the metal layer. The elastic dressing is provided with a surface which is suitable for the transfer of ink onto a print carrier. Furthermore, the dressing is provided with a nonslip coating which extends over part of the metal layer in one of the edge regions, in order to maintain the position of the dressing on the surface of the transfer cylinder during the rotation of the transfer cylinder. The nonslip layer has a higher coefficient of friction than that of the metal layer, and a thickness that is of a dimension sufficient for pushing the ends of the metal layer into the tensioning gap of the published European Patent Document EP 0 884 176 A1 is also concerned, furthermore, with a method for fastening a cylinder dressing on the transfer cylinder in the printing unit.
Starting from the prior art outlined hereinabove, it is an object of the invention to provide a fluid-loaded tensioning device for printing forms on rotary printing machines which serves, on one hand, for reliably interlocking tensioning elements for a printing form and, on the other hand, for ensuring that the tensioning elements are readily exchangeable.
With the foregoing and other objects in view, there is provided in accordance with one aspect of the invention, a tensioning device for a printing form on a jacket surface of a printing unit cylinder in a printing unit of a rotary printing machine, the printing unit cylinder being formed with a tensioning gap for receiving ends of the printing form therein, a tensioning shaft being received in a bore formed in the printing unit cylinder, the tensioning shaft being held under pretensioning by tensioning elements, comprising fluid-loaded cylinders disposed on the tensioning shaft for respectively locking and unlocking a tensioning element on the tensioning shaft, and a separate actuating cylinder for setting an operating pressure of the fluid-loaded cylinders.
In accordance with another feature of the invention, the tensioning shaft is formed with a bore connected in terms of pressure via a pressure line to a piston element of the separate actuating cylinder.
In accordance with a further feature of the invention, a piston element received in the separate actuating cylinder is connected to a force accumulator.
In accordance with an added feature of the invention, the tensioning device includes a chamber surrounding the piston element of the separate actuating cylinder, the chamber being pressure-loadable via a supply line.
In accordance with yet another feature of the invention, an axial actuating movement of the piston element of the actuating cylinder serves for generating a negative pressure in the bore formed in the tensioning shaft.
In accordance with yet a further feature of the invention, the bore and the actuating cylinder of the tensioning shaft are provided with aerating and deaerating bores, respectively.
In accordance with yet an added feature of the invention, the piston element has a part thereof formed with a diameter for controlling a fluid system formed of the bore in the tension shaft and the pressure line, the diameter being considerably smaller than the diameter of the rest of the piston element in the actuating cylinder.
In accordance with yet an additional feature of the invention, the piston element, when operative, releases the tensioning element on the tensioning shaft.
In accordance with still another feature of the invention, the piston element, when operative, causes a locking mechanism to move back out of said orifices formed in the tensioning element.
In accordance with still a further feature of the invention, the tensioning shaft and the separate actuating cylinder are received in orifices disposed independently of one another on the printing form cylinder.
In accordance with still an added feature of the invention, the tensioning device for a printing form includes a device disposed on one end face of the cylinder for manually operating the piston element.
In accordance with still an additional feature of the invention, the manually operating device includes a slotted guide for transmitting a tensile force.
In accordance with another feature of the invention, the tensioning device for a printing form includes a spring-loaded actuating element disposed on an end face of the cylinder for maintaining constant the tension of the printing form on the printing unit cylinder.
In accordance with a further aspect of the invention, there is provided a printing unit cylinder in the printing unit of a rotary printing machine, with a tensioning device for a printing form on a jacket surface of the printing unit cylinder, the printing unit cylinder being formed with a tensioning gap for receiving ends of the printing form therein, a tensioning shaft being received in a bore formed in the printing unit cylinder, the tensioning shaft being held under pretensioning by tensioning elements, comprising fluid-loaded cylinders disposed on the tensioning shaft for respectively locking and unlocking a tensioning element on the tensioning shaft, and a separate actuating cylinder for setting an operating pressure of the fluid-loaded cylinders.
In accordance with an added aspect of the invention, there is provided a printing unit of a rotary printing machine, with at least one printing unit cylinder formed with a tensioning gap for receiving ends of the printing form therein, a tensioning shaft received in a bore formed in the printing unit cylinder, the tensioning shaft being held under pretensioning by tensioning elements, comprising fluid-loaded cylinders disposed on the tensioning shaft for respectively locking and unlocking a tensioning element on the tensioning shaft, and a separate actuating cylinder for setting an operating pressure of the fluid-loaded cylinders.
In accordance with a concomitant feature of the invention, there is provided a printing unit cylinder in a printing unit of a rotary printing machine, cooperatively engaging with a transfer cylinder having a gapless covering disposed thereon, the printing unit cylinder being formed with a tensioning gap for receiving ends of the printing form therein, a tensioning shaft received in a bore formed in the printing unit cylinder, the tensioning shaft being held under pretensioning by tensioning elements, comprising fluid-loaded cylinders disposed on the tensioning shaft for respectively locking and unlocking a tensioning element on the tensioning shaft, and a separate actuating cylinder for setting an operating pressure of the fluid-loaded cylinders.
There are diverse advantages which can be afforded by the invention according to the instant application. The release of the edges of a printing form and the release of a tensioning element received in the tensioning gap of a printing unit cylinder can now be performed without requiring a tool, and without having to carry out initially a complicated removal of the mechanism in the periphery of the tensioning gap. Through the intermediary of a pneumatically operatable actuating cylinder embedded in the printing form cylinder, an extremely rapid response of a fluid system independent of the pneumatics can be achieved. The relatively long actuating travel distance of a piston element provided in the actuating cylinder can be converted into a plurality of adjusting operations taking place simultaneously in the tensioning gap of a printing form cylinder. The simultaneous execution of the unlocking movement can follow extremely quickly, so that it is possible to remove the released tensioning element from the tensioning gap in a very simple manner. The tensioning element is locked in the tensioning gap by a force accumulator displaced in the actuating cylinder, so that, even if the pneumatics fail, the arrest or retention of the tensioning element remains assured.
In a further embodiment of the concept upon which the invention is based, the actuating cylinder in the printing form cylinder is connected via a pressure line to a bore formed in the tensioning shaft for the tensioning element. The separation of the spatial arrangement of the actuating cylinder and the fluid system for locking and unlocking the tensioning element on the tensioning shaft permits rather simple manufacture, because sufficient construction space is available on the printing form cylinder. The separate actuating cylinder is provided with a piston element which is loaded by a force accumulator. Via a piston surface, the force accumulator acts upon the fluid contained in the fluid system and loads the latter in a manner that the interlocking of the tensioning elements is assured at all times during the rotation of the printing unit cylinder. On the other hand, the piston element is loaded via a pressure delivery line terminating separately in the actuating cylinder, in order to produce a pressure drop in the fluid system operating the tensioning element.
Due to the pressure drop capable of being generated in the fluid system made up of the bore passing through the tensioning shaft, and the flexible outer supply line, the bolt elements locking the tensioning element are withdrawn and release orifices in formed the tensioning element, with the result that it becomes possible for the tensioning element to be removed from the tensioning gap of the printing form cylinder.
The piston element in the actuating cylinder has formed thereon, on the one hand, the active surface which controls the movement of the locking/unlocking elements and, on the other hand, also the surface which, loaded by a pressure capable of being generated pneumatically, moves the piston surface acting upon the fluid system.
In order to uncouple the control systems inside the printing form cylinder, the actuating cylinder and the tensioning shaft are accommodated on one side of the printing unit cylinder in installation spaces independent of one another. The systems are connected to one another via a high-pressure line lying outside on the end face of the printing unit cylinder.
For manual operation of the actuating cylinder, a lever element may be provided on the opposite end face of the printing form cylinder and, co-operating with a slotted guide, ensures the manual movability of the piston element, so that the latter can also be operated manually in an emergency. The device according to the invention can be incorporated in a printing unit cylinder, the latter being capable of being used both in the printing unit of a sheet-processing rotary printing machine and in the printing unit of a web-processing rotary printing machine. Furthermore, a printing unit cylinder equipped with the device proposed in accordance with the invention can be used perfectly well in a printing unit having a transfer cylinder which is provided with a gapless covering exchangeable through an orifice or opening formed in the side wall of the printing unit.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a fluid-loaded tensioning device for printing forms on rotary printing machines, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.